BBM is a cross-platform messaging service that allows users to converse with their friends, whether they are using BlackBerry, Android or iOS-based hardware.

Much like rival service WhatsApp, the application alerts users when their messages have been delivered and read, and shows them when their contacts are typing out a response.

Sharing files is also supported, with subscribers able to send photos, documents, voice notes and more to their friends. They can also punctuate their messages with a raft of emoticons.

BBM is always on and always connected, a feature which comes with both pros and cons. While there is no need to open the app to check messages, users will have to live with an ever-present BBM icon in their notifications bar while the app is running.

Video sharing, voice calls, and the option to share contacts and calendar events are among the glaring omissions at launch.

Group chat features

BBM allows subscribers to take part in group chats to share messages and files with multiple people at once.

They can invite multiple friends into a group of their own creation, and even take part in conversations with users who are not listed among their contacts. It's all fairly standard, yet essential stuff.

Privacy features and user interface

BlackBerry has long prided itself on its watertight security, and BBM values privacy above all else.

Rather than using email addresses or phone numbers like many of its competitors, BBM assigns users with a PIN, giving them total control over who can contact them. Adding contacts is a two-way opt-in process, so you won't find yourself bombarded by unwanted messages.

Since BBM is bound to your registration details, multiple device logins are not supported simultaneously, a feature which some of its competitors do offer.

BB10's users interface and layout are based on the BlackBerry 10 mobile operating system, with gesture-based controls and slide-out panes and panels.

As neither iOS nor Android uses pop-out menus in this way, users are likely to experience some initial culture shock, but navigating menus is pleasingly fast and straightforward once you have acclimatised.

The BBM app requires a 13MB download on Android, and a 31.2MB download on iOS.

Anticipating high demand, BlackBerry has implemented a waiting list system to ensure that the service's multi-platform rollout goes smoothly, which unfortunately means that customers who didn't sign up in advance are in for a short wait post-install.

Once your registered email address reaches the front of the queue, setup is a painless process, with users needing only to choose a BlackBerry ID and input a couple of personal details before they are up and running.

BlackBerry legacy users can even port over their old account details at the touch of a button.

Should I download BBM?

The usefulness of a messaging application depends primarily on one factor - do your friends and acquaintances use the same platform?

If the answer to the above question is yes, then there is really no reason to overlook BBM since it's well-designed and speedy to navigate.

However, given that BlackBerry's user base has been in decline for some time, the chances are that many of your contacts have already pledged unwavering allegiance to competitors such as WhatsApp and Kik Messenger.